There was no precedent to check for a double digit point release since IIRC Apple had never used one prior to 10.10 (9.2.2, 8.6, 7.6, 6.0.8, 5.1, 4.1, etc.). Mac OS X 10.10 was released 3 years after Pro Tools 9.0.6 which was only qualified on Mac OS X 10.6-10.7.4. If it helps, Pro Tools 9 can be
upgraded to current to run on a newer OS.